1. Field of the Invention
The present invention relates to a control device and a method for controlling a variable valve timing mechanism which varies valve timing of an engine valve (an intake valve or an exhaust value) of an internal combustion engine.
2. Description of Related Art
A control device of this type of variable valve timing mechanism controls a valve timing by detecting the rotation phase of a camshaft with respect to a crankshaft and bringing the rotation phase close to a target rotation phase by using the variable valve timing mechanism.
However, the crankshaft may rotate in a reverse direction to a forward rotation direction (reverse rotation) at a time of extremely low rotation of an engine just before a stopping, such as when operation of the engine is stopped. In a technique disclosed in Japanese Laid-Open Patent Publication 2000-303865, since the rotation phase of a camshaft cannot be correctly detected when reverse rotation is detected, feedback control to the target phase is stopped and an intake camshaft is driven to rotate to a reference rotation angle position (a default position) where an intake camshaft impacts a stopper in the retard angle direction by a variable valve timing mechanism until the engine is stopped.
However, since the closing timing of the intake valve (IVC) moves away from the dead center of the intake bottom, the effective stroke decreases, the intake air amount decreases and thereby the startability during the next startup decreases at the reference rotation angle position retarded in angle as described above.